Serpent

IntroductionSerpent is a drawless annihilation game for two players: Black and White. It is played on the hexes (cells) of an initially empty hexagonal board. The recommended size is 5 cells per side, although 4 and 6 are also valid. Each player has a sufficient supply of stones of their own color. Definitions: A snake is a maximal set of connected stones of the same color, whose stones are adjacent to no more than two stones of that snake that are not adjacent to each other. A single stone is an egg. An end is a stone of the snake that is adjacent to exactly one stone of the same snake. The head of a snake is the end with the shortest survival path to the end or egg of another friendly snake. The other end is the tail. If both ends have survival paths of equal length, either one may be the head and the other the tail. A survival path is a continuous sequence of empty cells from an egg, head, or tail of a snake to an egg, head, or tail of another friendly snake, such that, by filling the sequence and the ends with friendly stones, a single valid snake would be created. An egg or snake is alive if it has a survival path to an egg, head, or tail of another friendly snake; otherwise, it is dead. A group is also alive if there has never been more than one group of its color on the board. Turns:Black plays first, then turns alternate. On your turn, perform one of the following actions: Place a stone of your color on an empty cell adjacent to at most two friendly eggs and to no friendly snake. Move a friendly snake's tail to an empty cell adjacent to its head. The move is valid only if, after all the removals, the snake maintains a shorter survival path than the previous one, which can reach 0 cells in length. At the end of your turn, choose a color and remove all eggs and dead snakes of that color simultaneously, then do the same with the other color. A removal is valid only if it creates a connected set of empty cells in which its owner cannot play on the next turn, invalidating any dead formations that cannot be removed under this condition. If the only stone removed is the one you just placed, your placement is illegal. End of the game:You win if the last enemy egg or snake is removed from the board. —description from the designer